In vacuum toilet systems, especially for marine use, and for use in other vehicles such as RVs, it is desirable to provide as few components as possible, and to make the systems as inexpensive as possible while still being capable of performing the intended functions in a highly effective manner. This has led to the development of advanced systems which use a single tank as both a vacuum reservoir to effect quick and effective flushing, and as a holding tank for the sewage from the one or more toilets of the system, such as shown in U.S. Pat. No. 5,681,148 (the disclosure of which is hereby incorporated by reference herein) and U.S. Pat. No. 4,713,847. While such new technology is highly effective, it cannot be easily or cost effectively retrofit to more traditional systems, such as shown in U.S. Pat. No. 4,819,279. Also for some installations a simpler arrangement is desired than in said U.S. Pat. Nos. 5,681,148 and 4,713,847.
According to the present invention a simple system, and method of utilization thereof, are provided which can turn a conventional VHT holding tank into a combined vacuum and holding tank, thereby saving space, which is at a premium in many vacuum tank installations, such as on boats. Simply by adding a conventional three way valve, either manually or automatically operated, and utilizing a pump capable of pumping both air and sewage, a cost effective and highly functional system and method may be provided both for retrofitting existing installations, and for new installations.
According to one aspect of the present invention there is provided a vacuum toilet system comprising: At least one vacuum toilet. A combination sewage holding and vacuum tank operatively connected to the vacuum toilet, the tank having a top and a bottom. A pump capable of pumping air and sewage. An air conduit connected to the tank adjacent the top thereof at a first end, and having a second end. A sewage conduit having a bottom end positioned adjacent the tank bottom, and a top end connected to the pump. The air conduit second end operatively connected to the sewage conduit between the top and bottom ends thereof. A valve connected to the air conduit between the air conduit first end and the sewage conduit, the valve having: a first position in which atmospheric air can pass through the valve into the tank through the air conduit first end, but not directly to the pump; and a second position in which air from the tank passes through the air conduit first end directly to the pump and atmospheric air is substantially precluded from entering the air conduit. A vacuum switch for sensing vacuum level in the tank and controlling the pump in response thereto when the valve is in the second position. And, a second switch for operating the pump when the valve is in the first position for pumping sewage out of the tank. The pump may comprise a bellows operated pump with an inlet (and outlet) containing two in series check valves (each), such as duckbill valves. A preferred commercially available pump is an S-series pump available from Sealand Technology, Inc. of Big Prairie, Ohio.
The valve may be of the type conventionally known as a three way valve, preferably a ball valve, which has a single outlet and two inlets (with or without a completely xe2x80x9coffxe2x80x9d position). The valve may be manually operated, or automatically (e.g. solenoid) operated depending upon other components of the system and the degree of complexity and level of expense desired or acceptable.
The system may further comprise a float switch for detecting the level of sewage in the tank, the float switch comprising the second switch. In this case typically the valve is a solenoid operated valve which is controlled by the second switch to move the valve to the first position. The system may still further comprise a manually operated switch to control operation of the pump to effect sewage pumpout. In this latter case the valve is controlled by operation of the float switch or the manually operated switch to automatically move to the first position.
Alternatively the second switch may comprise a manually operated switch. The system may then further comprise a float switch which senses the level of sewage in the tank and when a predetermined level is sensed precludes operation of the pump until the valve is in the first position and the second switch is manually activated.
Typically the tank has a top surface and a hollow extension extending above the top surface; and the vacuum switch and air conduit first end are connected to the hollow extension. In this case the second switch may comprise a float switch including a component extending downwardly from the interior of the top surface into the tank.
According to another aspect of the present invention there is provided a method of operating a combined vacuum and holding tank of a vacuum toilet system having a pump capable of pumping either air and sewage, and a multi-position valve, comprising: (a) Sensing the vacuum level in the tank. (b) When the level sensed in (a) is below a predetermined amount controlling the position of the valve and pumping air from the tank through the valve using the pump, until the desired level is reached, and then stopping air pumping using the pump. And, (c) when emptying sewage from the tank is desired, controlling operation of the pump and the position of the valve so that the sewage is pumped from the tank through the pump, and air passes from the atmosphere through the valve into the tank.
Preferably (b) is practiced to operate the pump to pull air from the tank through the valve when the vacuum level in the tank is less than about 10 inches of mercury. Also in the method (b) and (c) may be practiced in part by moving the valve to the desired position manually. Also (c) may be practiced by manually activating a switch to start operation of the pump when the valve is in a position to allow air flow into the tank from the surrounding environment.
It is the primary object of the present invention to provide a simple, versatile, and cost effective vacuum toilet system and method of utilization thereof. This and other objects of the invention will become clear from a detailed description of the invention and from the appended claims.